The part number on that Hitachi 4gb Microdrive is below. I had a friend (same one who is attempting the bluetooth hack for me on my 6k- I wish all my friends were like him!) who recently gifted me with one. He purchased it from newegg.com, they had it on sale for $103. 10 mins after he ordered mine they were no longer in stock.

Here's the info (and it works great in our families 6000L's (sharp rom currently)):

The antistatic bag within the packaging reads:

MODEL: HMS360604D5CF00P/N: 0A40241

The actual blisterpack that it came in- You WILL need a jackhammer and possibly heavy earth-moving equipment to get into the package, gives the following info:

EDIT: I looked back at the packaging- can't tell for sure but it looks like the info label on the anti-static bag MIGHT have been readable through a cutout in the packaging's cardboard, so hopefully you CAN read it b4 you buy.

This was the retail version. I have been told that the OEM version DEFINITELY does NOT work. Can't confirm/deny that myself.

Hope this info helps!

-NeuroShock

EDIT: I found out that how you can tell for SURE if you've got the correct 4gb or 6gb Hitachi Microdrive- by insuring it's sold in a blister-pack by the Company called Pexagon Technology Inc. that I listed above. It appears that Pexagon is partnered with Hitachi and does ALL retail sales for them. The Pexagon part number is MD4GB-BP. My guess is that the 6gb model would have the part number MD6GB-BP. Regardless any Hitachi Microdrive sold by Pexagon in a blisterpack WILL WORK with the Zaurus SL-6000L models, and It's been my experience that if it works with the 6k it usually will work with all clamshell models as well. I haven't tried it with my 5500's, and don't own a 5600 so I cannot speak for that either.